bpo-40291: Add support for CAN_J1939 sockets (GH-19538)

Add support for CAN_J1939 sockets that wrap SAE J1939 protocol
functionality provided by Linux 5.4+ kernels.

Lib/test/test_socket.py

@@ -80,6 +80,16 @@ def _have_socket_can_isotp():
         s.close()
     return True
 
+def _have_socket_can_j1939():
+    """Check whether CAN J1939 sockets are supported on this host."""
+    try:
+        s = socket.socket(socket.PF_CAN, socket.SOCK_DGRAM, socket.CAN_J1939)
+    except (AttributeError, OSError):
+        return False
+    else:
+        s.close()
+    return True
+
 def _have_socket_rds():
     """Check whether RDS sockets are supported on this host."""
     try:
@@ -143,6 +153,8 @@ HAVE_SOCKET_CAN = _have_socket_can()
 
 HAVE_SOCKET_CAN_ISOTP = _have_socket_can_isotp()
 
+HAVE_SOCKET_CAN_J1939 = _have_socket_can_j1939()
+
 HAVE_SOCKET_RDS = _have_socket_rds()
 
 HAVE_SOCKET_ALG = _have_socket_alg()
@@ -2117,6 +2129,68 @@ class ISOTPTest(unittest.TestCase):
                 raise
 
 
+@unittest.skipUnless(HAVE_SOCKET_CAN_J1939, 'CAN J1939 required for this test.')
+class J1939Test(unittest.TestCase):
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.interface = "vcan0"
+
+    @unittest.skipUnless(hasattr(socket, "CAN_J1939"),
+                         'socket.CAN_J1939 required for this test.')
+    def testJ1939Constants(self):
+        socket.CAN_J1939
+
+        socket.J1939_MAX_UNICAST_ADDR
+        socket.J1939_IDLE_ADDR
+        socket.J1939_NO_ADDR
+        socket.J1939_NO_NAME
+        socket.J1939_PGN_REQUEST
+        socket.J1939_PGN_ADDRESS_CLAIMED
+        socket.J1939_PGN_ADDRESS_COMMANDED
+        socket.J1939_PGN_PDU1_MAX
+        socket.J1939_PGN_MAX
+        socket.J1939_NO_PGN
+
+        # J1939 socket options
+        socket.SO_J1939_FILTER
+        socket.SO_J1939_PROMISC
+        socket.SO_J1939_SEND_PRIO
+        socket.SO_J1939_ERRQUEUE
+
+        socket.SCM_J1939_DEST_ADDR
+        socket.SCM_J1939_DEST_NAME
+        socket.SCM_J1939_PRIO
+        socket.SCM_J1939_ERRQUEUE
+
+        socket.J1939_NLA_PAD
+        socket.J1939_NLA_BYTES_ACKED
+
+        socket.J1939_EE_INFO_NONE
+        socket.J1939_EE_INFO_TX_ABORT
+
+        socket.J1939_FILTER_MAX
+
+    @unittest.skipUnless(hasattr(socket, "CAN_J1939"),
+                         'socket.CAN_J1939 required for this test.')
+    def testCreateJ1939Socket(self):
+        with socket.socket(socket.PF_CAN, socket.SOCK_DGRAM, socket.CAN_J1939) as s:
+            pass
+
+    def testBind(self):
+        try:
+            with socket.socket(socket.PF_CAN, socket.SOCK_DGRAM, socket.CAN_J1939) as s:
+                addr = self.interface, socket.J1939_NO_NAME, socket.J1939_NO_PGN, socket.J1939_NO_ADDR
+                s.bind(addr)
+                self.assertEqual(s.getsockname(), addr)
+        except OSError as e:
+            if e.errno == errno.ENODEV:
+                self.skipTest('network interface `%s` does not exist' %
+                           self.interface)
+            else:
+                raise
+
+
 @unittest.skipUnless(HAVE_SOCKET_RDS, 'RDS sockets required for this test.')
 class BasicRDSTest(unittest.TestCase):